The cellular/molecular abnormalities of Alzheimer's disease are also present in older patients with Down's syndrome and in some old nondemented individuals. To evaluate these changes, it is essential to have optimally prepared tissues from clinically well-characterized cases who lack other confounding illnesses. Core C includes a staff of neuropathologists, neuroanatomists, other basic scientists, a clinical coordinator, and technical personnel. The professional staff of Core C arranges autopsies, neuropathological diagnosis, and coordinates the use of tissues for research. These scientists also direct the technical staff and laboratory facilities involved in histology, immunocytochemistry, neurochemistry, receptor autoradiography, and computer-assisted imaging (i.e., for morphometry, autoradiography, in situ hybridization, and Northern and Western blots). The clinical coordinator works with patients, families, and clinicians to facilitate autopsies. The technical staff assists with autopsy procedures and brain dissections, performs histological processing and staining of diagnostic and research material, accessions and stores tissues for distribution to investigators, assists with preparation of tissues or neurochemical and autoradiographic studies, and maintains and operates the image analysis systems. Finally, members of the Core C staff participate in projects of the Consorium to Establish a Registry for Alzheimer's Disease (CERAD) and contribute significantly to the training of physicians and scientists on issues relevant to aging, Alzheimer's disease, and Down's syndrome.